Method for providing an M2M service, and method and apparatus for M2M communication

ABSTRACT

Provided is a method for machine to machine (M2M) communication. An M2M device acquires an M2M group identification (MGID) and an M2M zone identification. The M2M device checks whether or not the M2M device has escaped from the M2M group zone. If the M2M device has escaped from the M2M group zone, the M2M device transmits, to a base station, an update request message which requests that the M2M group identifier be updated. The M2M device receives, from the base station, a response message as a response to the update request message.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2012/007220, filed on Sep. 7, 2012,which claims the benefit of U.S. Provisional Application Ser. No.61/532,572, filed on Sep. 9, 2011, the contents of which are all herebyincorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to wireless communication, and moreparticularly, to a method for resuming a machine to machine (M2M)service in a wireless communication system and an M2M device thatoperates according to the method.

2. Related Art

With the development of wireless communication technology, notcommunications between a general user and a base station, but varioustypes of wireless communication systems appear.

Machine to machine (M2M) communication is also referred to as machinetype communication (MTC) and is one type of data communication includingone or more entities that dos not require human interaction. That is,the M2M communication is called a concept that not a terminal used byhuman but a machine device performs communication by using the existingwireless communication network. The machine device used in the M2Mcommunication is referred to as an M2M device. The M2M device includesvarious devices including a vending machine, an electricity meter, amachine for measuring a water level of a dam, and the like.

Since a characteristic of the M2M device is different from that of ageneral terminal, a service optimized for the M2M communication may bedifferent from a service optimized for human to human communication. TheM2M communication may be characterized by different market scenarios,data communication, low cost and small efforts, potentially a lot of M2Mdevice, a wide service zone, and low traffic per M2M device as comparedwith a current mobile network communication service.

Meanwhile, the M2M device may have much lower or higher mobility thanthe terminal. When the M2M device escapes from a service zone, a methodfor efficiently resuming the service is required.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method for resuming amachine to machine (M2M) service based on a serviceunavailability/resuming indication message and an M2M device thatoperates according to the method.

In accordance with an aspect of the present invention, there is provideda method for providing, a base station, a machine to machine (M2M)service in M2M communication. The method may include: Receiving anupdate request message of requesting updating an M2M group identifier(MGID) from an M2M device, wherein the update request message includesan M2M group identifier and an M2M zone identifier, the M2M groupidentifier identifies a service flow shared by a group of M2M devices inan M2M group zone, and the M2M zone identifier identifies the M2M groupzone; and transmitting a response message to the update request messageto the M2M device, wherein the response message includes a serviceunavailability indicator that indicates whether the service flowidentified by the M2M group identifier is provided in a zone indicatedby the M2M zone identifier.

In accordance with another aspect of the present invention, there isprovided a method for machine to machine (M2M) communication by an M2Mdevice. The method may include: acquiring an M2M group identifier (MGID)and an M2M zone identifier, wherein the M2M group identifier identifiesa service flow shared by a group of M2M devices in an M2M group zone andthe M2M zone identifier identifies the M2M group zone; verifying whetherthe M2M device escapes from the M2M group zone; transmitting an updaterequest message of requesting updating the M2M group identifier when theM2M device escapes from the M2M group zone; and receiving a responsemessage as a response to the update request message from the basestation, wherein the response message includes a service unavailabilityindicator that indicates whether the service flow identified by the M2Mgroup identifier is provided in a zone indicated by the M2M zoneidentifier.

In accordance with yet another aspect of the present invention, there isprovided a machine to machine (M2M) device in an M2M communicationsystem. The M2M device includes a radio frequency (RF) unit transmittingor receiving a radio signal; and a processor connected to the RF unit.The processor may acquires an M2M group identifier (MGID) and an M2Mzone identifier, wherein the M2M group identifier identifies a serviceflow shared by a group of M2M devices in an M2M group zone and the M2Mzone identifier identifies the M2M group zone; verifies whether the M2Mdevice escapes from the M2M group zone; transmits an update requestmessage of requesting updating the M2M group identifier when the M2Mdevice escapes from the M2M group zone; and receives a response messageas a response to the update request message from the base station,wherein the response message includes a service unavailability indicatorthat indicates whether the service flow identified by the M2M groupidentifier is provided in a zone indicated by the M2M zone identifier.

When a machine to machine (M2M) device escapes from a service zone, aservice can be efficiently resumed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates one example of machine to machine (M2M)communication.

FIG. 2 illustrates one example of a frame structure of an IEEE 820.16m.

FIG. 3 illustrates an operation transition diagram in the IEEE 802.16m.

FIG. 4 is a flowchart illustrating an operation in an idle mode in theIEEE 802.16m.

FIG. 5 and FIG. 6 illustrate scenarios based on a position of an M2Mserver defined by a WiMAX forum.

FIG. 7 illustrates a case in which an M2M device escapes from an M2Mservice zone.

FIG. 8 illustrates a flowchart for resuming an M2M service when an M2Mdevice escapes from an M2M group zone according to an embodiment of thepresent invention.

FIG. 9 illustrates a flowchart for resuming the M2M service when the M2Mdevice reenters the M2M group zone according to an embodiment of thepresent invention.

FIG. 10 illustrates a flowchart for resuming an M2M service when an M2Mdevice escapes from an M2M group zone according to another embodiment ofthe present invention.

FIG. 11 illustrates a flowchart for providing the M2M service by a basestation in M2M communication according to an embodiment of the presentinvention.

FIG. 12 illustrates a flowchart for M2M communication by the M2M deviceaccording to an embodiment of the present invention.

FIG. 13 is a block diagram illustrating a wireless communication systemin which an embodiment of the present invention is implemented.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 illustrates one example of machine to machine (M2M)communication.

The M2M communication is also referred to as machine type communication(MTC), and represents information exchange between M2M devices 11 and 12through a base station 15 which accompanies human interaction orinformation exchange between the M2M device 11 and an M2M server 18through the base station.

The M2M server 18 is an entity that communicates with the M2M device 11.The M2M server executes an M2M application and provides an M2M specificservice to the M2M device 11.

The M2M device 11 as a wireless device that provides the M2Mcommunication may be fixed or movable. The M2M device is also referredto as an MTC device.

The service provided through the M2M communication has a differentiationfrom a service in communication interfered by human in the related andincludes various categories of services including tracking, metering,payment, a medical field service, remote control, and the like.

Representative examples of individual service requirements of M2Mfeatures will be described below.

1) Time controlled feature: represents that the M2M device transmits ordevices data in only a predetermined specific section. Accordingly, itis possible to prevent unnecessary signaling outside the predeterminedspecific section.

2) Time tolerant feature: represents that the M2M device may delaytransferring data. A network operator may restrict the access of the M2Mdevice to a network or transmission of data to another MTC device anddynamically restrict the amount of data which the MTC device maytransfer in a specific zone.

3) Offline indication feature: represents that notification is requestedto the M2M device an appropriate time when signaling is not enabledbetween the M2M device and the network.

4) Priority alarm message (PAM) feature: represents that when anemergency situation in which the M2M device requests burglary,vandalism, or immediate caution occurs, the M2M device preferentiallywarns the network about the emergency situation.

Layout of hundreds to thousands of M2M devices in one cell (or basestation) is considered. Accordingly, since it is difficult to identifythe M2M device by only existing terminal identifiers, identifiersdescribed below are considered.

Station identifier (STID): represents an identifier that identifies theM2M device in a domain of the base station. The base station mayallocate the same STID to a plurality of M2M devices.

M2M group identifier (MGID): The MGID is a 12-bit identifier used touniquely identify a multicast service flow shared by a group of the M2Mdevices in the M2M group zone. The M2M group zone is a logical zoneincluding one or more base stations. The M2M group zone is identified byan M2M group zone index. The MGID is assigned during a dynamic serviceaddition (DSA) process. If the M2M device escapes from the network orthe service flow is not deleted, the M2M device retains the MGID in anidle mode.

Fixed M2M deregistration identifier (FMDID): represents a 16-bitidentifier used to uniquely identify the M2M device in a zone of thebase station. The FMDID is assigned to the M2M device during idle modeentry and released while the M2M device reenters the network.

Hereinafter, an idled mode operation in an IEEE 802.16m based systemwill be described with reference to Clause 16.2.18 of IEEE (Institute ofElectrical and Electronics Engineers) P802.16m/D10 “Part 16: AirInterface for Broadband Wireless Access Systems Advanced Air Interface”disclosed on Feb. 17, 2011. However, the wireless communication systemaccording to the present invention is not limited to the IEEE 802.16mbased system and may be applied to various wireless communicationsystems including 3GPP (3rd Generation Partnership Project) LTE (longterm evolution), and the like.

FIG. 2 illustrates one example of a frame structure of an IEEE 820.16m.

A superframe (SF) includes a superframe header (SFH) and four frames(including F0, F1, F2, and F4). All of the lengths of the respectiveframes in the superframe may be the same as each other. The size of thesuperframe is 20 ms and the size of each frame is 5 ms.

The frame includes a plurality of subframes SF0, SF1, SF2, SF3, SF4,SF5, SF6, and SF7. The subframe may be used for uplink transmission ordownlink transmission. The subframe includes a plurality of orthogonalfrequency division multiplexing (OFDM) symbols in a time domain. TheOFDM symbol is used to express one symbol period and multiple accessmethods are not limited in terms of a name thereof.

The subframe includes 6 OFDM symbols. This is just exemplary and thesubframe may include 5, 7, or 9 OFDM symbols and the present inventionis not limited thereto.

A type of the subframe may be defined according to the number of theOFDM symbols included in the subframe. For example, it may be definedthat a type-1 subframe includes 6 OFDMA symbols, a type-2 subframeincludes 7 OFDMA symbols, a type-3 subframe includes 5 OFDMA symbols,and a type-4 subframe includes 9 OFDMA symbols.

A time division duplex (TDD) method or a frequency division duplex (FDD)method may be applied to the frame. Subframes in the TDD frame may bedivided into uplink subframes and downlink subframes.

The size of the superframe, the number of the frames included in thesuperframe, the number of the subframes included in the frame, and thenumber of the OFDM symbols in the subframe may be changed and thepresent invention is not limited thereto.

The SFH may transport essential system parameter and systemconfiguration information. The SFH may be transmitted in five last OFDMsymbols of a first subframe in the superframe.

A physical resource unit (PRU) as a basic resource assignment unitincludes 18 subcarriers in consecutive OFDM symbols of the samesubframe.

In an IEEE 802.16 system, an advanced-MAP (A-MAP) transports servicecontrol information. A non-user specific A-MAP transports informationwhich is not limited to a specific user or a specific user group. Ahybrid automatic repeat request (HARQ) feedback A-MAP transports HARQACK/NACK information regarding uplink data transmission. A power controlA-MAP transports a power control command to a mobile station (MS).

An assignment A-MAP transports resource assignment information. Theassignment A-MAP includes several types including a downlink (DL) basicassignment A-MAP, an uplink (UL) basic assignment A-MAP, a code divisionmultiple access (CDMA) assignment A-MAP, and the like.

The CDMA assignment A-MAP includes UL resource assignment depending on abandwidth request or UL resource assignment depending on a rangingrequest.

All of the A-MAPs share a physical resource region called an A-MAPregion. The A-MAP region is present for each downlink subframe.

FIG. 3 illustrates an operation transition diagram in the IEEE 802.16m.

In an initialization state, the mobile station (MS) performs cellselection by receiving synchronization and system configurations.

In an access state, the mobile station performs the network entry. Thenetwork entry is a procedure including ranging with the base station,basic capability negotiation, and authentication.

In a connected state, the mobile station operates in one of a sleepmode, an active mode, and a scanning mode. During the connected state,the mobile station retains a connection established during the accessstate. The mobile station in the active mode may continuously transmitor receive scheduled data. In the sleep mode, a radio frame is dividedinto a sleep window and a listening window. The mobile station in thesleep mode may receive data from the base station during the listeningwindow. The mobile station in the scanning mode performs measurementindicated by the base station.

In the idle state, the mobile station operates in the idle mode. In theidle mode, a paging available interval and a paging unavailable intervalare provided. The base station does not transmit predetermined downlinktraffic such as a paging message in the paging unavailable interval.

FIG. 4 is a flowchart illustrating an operation in an idle mode in theIEEE 802.16m.

In step S410, the mobile station in the idle mode monitors receiving thepaging message during the paging available interval to receive a pagingadvertisement (PAG-ADV) message. The paging message is a notificationmessage that indicates whether downlink traffic pended to a specificmobile station is present.

The base station may indicate each mobile station to perform ranging fornetwork reentry or location update through the PAG-ADV message.

In step S420, when the PAG-ADV message requests the network reentry, themobile station ends the idle mode and transmits a ranging code to thebase station.

In step S430, the mobile station receives, from the base station, aranging-response (RNG-RSP) message as a response to the ranging code.The RNG-RSP message includes a status code. The status code indicatesone of ‘continue’, ‘success’, and ‘abort’.

When receiving the RNG-RSP message in which the status code is‘continue’, the mobile station transmits the ranging code again.

When the status code indicates ‘success’, the mobile station receivesthe assignment A-MAP. The assignment A-MAP includes the CDMA assignmentA-MAP.

In step S450, the mobile station transmits a ranging-request (RNG-REQ)message to the base station by using UL resource assignment indicated bythe CDMA assignment A-MAP.

In step S460, the mobile station receives the RNG-RSP message as aresponse to the RNG-REQ message.

Meanwhile, as described above, the M2M group identifier (MGID) is a12-bit identifier used to uniquely identify the M2M group in the domainof the network entity.

The MGID may be assigned to during dynamic service addition afterinitial network entry, and the M2M device may retain the MGID assignedduring the connected/idle mode. For example, the MGID may be assignedthrough mapping between the flow and the MGID in a connection additionstep.

The MGID may be released when entering an explicit network exit orderegistration with context retention (DCR) mode. Further, the MGID maybe deleted by a dynamic service deletion (DSD) procedure. For example,when the flow is deleted, the MGID may be released.

Meanwhile is updated based on the mode of the M2M device.

For example, when the M2M device is in the connected mode, the MGID ofthe M2M device may be updated by the dynamic service change (DSC)procedure or updated/added through an RNG-RSP message in a handover(HQ). The RNG-RSP represents a ranging response.

For example, when the mobile station is in the idle mode, the MGID ofthe M2M device may be updated through the location update or networkreentry. When MGIDs of all M2M devices in the group are intended to bechanged, the MGID of the M2M device may be updated by group locationupdate through the paging message. When time base update is performed,the MGID of the M2M device may be updated through the RNG-RSP message.

Meanwhile, a WiMAX forum defines two different scenarios based on theposition of the M2M server. FIGS. 5 and 6 illustrate two scenarios.According to the scenarios defined by the WiMAX forum, WiMAX operators500 and 600 include access service networks (ASN) 510 and 610 andconnectivity service networks (CSN) 520 and 620, as illustrated in FIGS.5 and 6. The ASN includes the base station and an access service networkgateway (ASN GW). The base station provides application services such asthe Internet, an application service such as VoIP, and a wireless accesswith the CSNs 520 and 620. The ASN GW controls the base station andtakes charge of connection with the CSNs 520 and 620. The CSNs 520 and620 provide a home agent function and authentication and chargingfunctions of a mobile IP.

M2M users 540 and 640 may communicate with the M2M servers 550 and 560through an web application programming interface (API). The web API isan opened API that allows a programmatic function to be easily usedoutside by providing an API through a web to develop a related service.

FIG. 5 illustrates a case in which the M2M server 550 is present in theCSN 520. FIG. 6 illustrates a case in which the M2M server 650 ispresent outside the CSN 620. In an example of FIG. 5, the M2M server 550is operated by the WiMAX operator 500, but in an example of FIG. 6, theM2M server 650 is not operated by the WiMAX operator 600.

According to the related art, the M2M group ID, that is, the MGID isassigned by the M2M network entity, but the M2M network entity is notdefined in detail. When an M2M subscriber (alternatively, user) providesthe M2M service to only an M2M device positioned in a specific region, aspecific M2M server may be connected to only a specific ASN.

Meanwhile, FIG. 7 illustrates a case in which the M2M device escapesfrom the M2M service zone.

According to the related art, in the case in which the M2M deviceescapes from the M2M service zone, for example, in the case in which theM2M device escapes from a domain of the network entity assigned with theMGID, when the escape is not recognized, a problem that data regarding awrong M2M service flow is received occurs.

Moreover, when the M2M device escapes from a current region where theMGID is available and thereafter, moves to a region where thecorresponding service is not provided, it needs to be considered thatthe MGID needs to be released.

Accordingly, the present invention provides a method for resuming an M2Mservice based on a service unavailability/resuming indication messageand an M2M device that operates according to the method.

Hereinafter, it is assumed that the M2M device knows a domain of anetwork entity assigned with its current MGID, that is, a domain wherethe current MGID is available.

For example, when the M2M device is allocated with the MGID, the M2Mdevice receives even an ID of an network entity that assigns the MGID.That is, the base station notifies to the M2M device the ID of thenetwork entity to which the base station belongs to allow the M2M deviceto recognize that the M2M device escapes from the domain of the networkentity.

As another example, the M2M device receives an even M2M zone identifierwhen being assigned with the MGID. Herein, the M2M zone identifier isused to identify the M2M zone and may mean the M2M group zone index.That is, the base station notifies to the M2M device the M2M zoneidentifier to allow the M2M device to recognize that the M2M deviceescapes from the domain of the network entity.

The M2M device may recognize all of the IDs (M2M zone identifiers) ofthe network entities regardless of the mode status, that is, regardlessof the connected mode or the idle mode.

FIG. 8 is a flowchart illustrating a method for resuming an M2M servicewhen an M2M device escapes from an M2M group zone.

In the case in which the M2M device escapes from the domain where thecurrent MGID is available, that is, the M2M device recognizes that theM2M device escapes from the M2M group zone, the M2M device may requestthe base station to update the MGID (S810).

When the base station is requested to update the MGID from the M2Mdevice, the base station judges whether the service flow used by thecorresponding M2M device may be provided within current coverage (S820).

If the service flow used by the M2M device may not be provided withinthe current coverage, the base station transmits a serviceunavailability indication message to the M2M device (S830).

The M2M device in the connected mode may receive the serviceunavailability indication through a DSC message.

The M2M device in the idle mode may receive the service unavailabilityindication in the MGID update procedure. For example, while the MGID isupdated in the location update or network reentry procedure, the M2Mdevice may receive the service unavailability indication. For example,when the M2M device requests updating the MGID through the RNG-REQmessage, the M2M device may receive the service unavailabilityindication through the response to message, that is, the RNG-RSP messageis used.

The M2M device that receives the service unavailability indicationrecognizes that the corresponding service is unavailable in a currentzone and defers the corresponding service flow (S840). In this case, theexisting MGID of the M2M device is not released but retained.

FIG. 9 is a flowchart illustrating a method for resuming the M2M servicewhen the M2M device reenters the M2M group zone according to anembodiment of the present invention.

As described in the example of FIG. 8, in the case in which the M2Mdevice escapes from the domain where the existing MGID is available,that is, the M2M group zone, the M2M device monitors whether to reenterthe M2M group zone (S900). For example, when the ID (alternatively, theM2M zone identifier) of the network entity is changed, the M2M devicemay verify whether to return to the domain where the existing MGID isavailable again.

As an embodiment, when the M2M device returns to the domain where theexisting MGID is available again, the M2M device transmits a serviceresuming request message to the base station (S911). The base stationjudges whether the M2M device may use the existing service flow by usingthe existing MGID as it is (S912). That is, the base station judgeswhether to provide a service flow based on the existing MGID. In thecase in which the existing MGID is usable, that is, in the case in whichthe service flow may be provided, the base station may notify to the M2Mdevice that the service may be resumed without updating the MGID orindicate that the service may be resumed by transmitting a serviceresuming message (S913). Finally, the M2M device resumes the service byusing the existing MGID (S914).

As another embodiment, when the M2M device returns to the domain wherethe existing MGID is available again, the M2M device judges whether touse the existing service flow by using the existing MGID as it is(S921). When the existing MGID is usable, the M2M device transmits aservice resuming notification message to the base station (S922).Further, the M2M device resumes the service by using the existing MGID(S923). Meanwhile, the M2M device may resume the service simultaneouslywith transmitting the service resuming notification message or firstresume the service and thereafter, notify the resumed service to thebase station. Further, the M2M device may judge whether to use theexisting service flow and/or resume the service immediately withouttransmitting the service resuming notification message. That is, theaforementioned steps (for example, steps S922 and S923) may be performedin different orders or simultaneously and some steps (for example, stepsS921 and/or S922) may be skipped.

FIG. 10 is a flowchart illustrating a method for resuming an M2M servicewhen an M2M device escapes from an M2M group zone according to anotherembodiment of the present invention.

Referring to FIG. 10, a step (step S1010) in which the M2M devicetransmits an MGID update request message to the base station, a step(S1020) in which the base station judges whether to provide the serviceflow used by the M2M device within the current coverage (S1020), and astep (S1030) in which the base station transmits the serviceunavailability indication message to the M2M device are the same orsimilar as the respective steps (S810 to S830) of FIG. 8.

Meanwhile, in the embodiment of FIG. 10, when receiving the serviceunavailability indication message, the M2M device may activate adiffered MGID retain timer together with deferring and retaining thecorresponding service flow (S1040). The deferred MGID retain timerindicates a time (alternatively, frame) of retaining the MGID when theservice flow is deferred. Hereinafter, an operation of the deferred MGIDretain timer will be described in more detail.

When the M2M device returns to the domain where the existing MGID isavailable, that is, the M2M group zone before the deferred MGID retaintimer is terminated, the M2M device ends the deferred MGID retain timerand resumes the service according to the embodiment (for example, stepsS911 to S914 and steps S921 to S923).

When the deferred MGID retain timer is terminated before the M2M devicereturns to the domain where the existing MGID is available, that is, theM2M group zone, the M2M device releases the MGID (S1050). The releasingprocess of the MGID may be performed in an IEEE 802.16 based DSDprocedure.

FIG. 11 is a flowchart illustrating a method for providing the M2Mservice by a base station in M2M communication according to anembodiment of the present invention.

The base station receives an update request message of requestingupdating the M2M group identifier (MGID) from the M2M device (S1110).The update request message may include the M2M group identifier and theM2M zone identifier. As described above, the M2M group identifieridentifies the service flow shared by the group of the M2M devices inthe M2M group zone and the M2M zone identifier identifies the M2M groupzone.

The base station judges whether the service flow identified by the M2Mgroup identifier is provided in the zone indicated by the M2M zoneidentifier based on the update request message (S1120).

The base station transmits a response message to the update requestmessage to the M2M device (S1130).

When the service flow is provided, the base station may transmit anupdate response message including a new M2M group identifier. When theservice flow is not provided, the base station may indicate to the M2Mdevice retaining of the M2M group identifier and deferring of theservice flow.

Whether the service flow is provided may be transferred by using aservice unavailability indicator. That is, the base station may transmita response message including the service unavailability indicator.

Meanwhile, the response message may be transmitted in an IEEE 802.16based DSC procedure or may mean a ranging-response (RNG-RSP) message.For example, when the M2M device is in the connected mode, the basestation may transmit the response message in the IEEE 802.16 based DSCprocedure. For example, when the M2M device is in the idle mode, theresponse message station may be an IEEE 802.16 based RNG-RSP message.

The service flow is not provided in the steps (S1110 to S1130), but whenthe M2M device moves to reenter the domain where the M2M groupidentifier is available, that is, the domain indicated by the M2M zoneidentifier, the base station may receive the service resuming requestmessage from the M2M device (S1140).

The base station may judge whether the service flow identified by theM2M group identifier is provided in the zone indicated by the M2M zoneidentifier again based on the service resuming request message and theupdate request message (S1150).

When the service flow is provided, the base station may transmit theservice resuming indication message to the M2M device (S1160).

FIG. 12 is a flowchart illustrating a method for M2M communication bythe M2M device according to an embodiment of the present invention.

The M2M device acquires the M2M group identifier (MGID) and the M2M zoneidentifier (S1210). As described above, the M2M group identifieridentifies the service flow shared by the group of the M2M devices inthe M2M group zone and the M2M zone identifier identifies the M2M groupzone.

The M2M device verifies whether the M2M device itself escapes from thezone indicated by the M2M zone identifier.

When the M2M device escapes from the zone indicated by the M2M zoneidentifier, the M2M device transmits to the base station the updaterequest message of requesting updating the M2M group identifier (S1230).

The M2M device receives the response message to the update requestmessage from the base station (S1240). As described above, the responsemessage may include the service unavailability indicator that indicateswhether the service flow identified by the M2M group identifier isprovided in the zone indicated by the M2M zone identifier.

Further, as described above, the response message may be transmitted inthe IEEE 802.16 based DSC procedure or may mean the ranging-response(RNG-RSP) message. For example, when the M2M device is in the connectedmode, the base station may transmit the response message in the IEEE802.16 based DSC procedure. For example, when the M2M device is in theidle mode, the response message may be the IEEE 802.16 based RNG-RSPmessage.

Meanwhile, when the service unavailability indicator indicates that theservice flow is not provided, the M2M device retains the M2M groupidentifier and defers the service flow (S1250). In this case, asdescribed above, the M2M device may active the deferred MGID retaintimer.

Thereafter, the M2M device monitors whether the M2M device itselfreenters the domain where the M2M group identifier is available, thatis, the zone indicated by the existing M2M zone identifier (S1260).

When reentering the zone indicated by the existing M2M zone identifier,the M2M device transmits to the base station the service resumingrequest message of requesting resuming the service flow (S1070). Whenreceiving the service resuming indication message as the response to theservicer resuming request message, the M2M device may resume theexisting service flow. Further, as described above, a method may beused, in which the M2M device does not transmit the service resumingrequest message but resume the service flow immediately under thejudgment of the M2M device.

On the contrary, when the M2M device does not reenter the zone indicatedby the existing M2M zone identifier before the deferred MGID retaintimer is terminated, the M2M device releases the MGID and ends thecorresponding service flow.

FIG. 13 is a block diagram illustrating a wireless communication systemin which an embodiment of the present invention is implemented.

An M2M device 50 includes a processor 51, a memory 52, and a radiofrequency (RF) unit 53. The memory 52 is connected with the processor 51to store various pieces of information for driving the processor 51. TheRF unit 53 is connected with the processor 51 to transmit and/or receivea radio signal. The processor 51 implements a function, a process,and/or a method which are proposed. In the embodiment, the operation ofthe MTC device may be implemented by the processor 51.

A base station 60 includes a processor 61, a memory 62, and an RF unit63. The memory 62 is connected with the processor 61 to store variouspieces of information for driving the processor 61. The RF unit 63 isconnected with the processor 61 to transmit and/or receive the radiosignal. The processor 61 implements a function, a process, and/or amethod which are proposed. In the embodiment, the operation of the basestation may be implemented by the processor 61.

The processor may include an application-specific integrated circuit(ASIC), another chip set, a logic circuit and/or a data processingapparatus. The memory may include a read-only memory (ROM), a randomaccess memory (RAM), a flash memory, a memory card, a storage medium,and/or another storage device. The RF unit may include a basebandcircuit for processing the radio signal. When the embodiment isimplemented by software, the aforementioned technique may be implementedby a module (a process, a function, and the like) that performs theaforementioned function. The module may be stored in the memory andexecuted by the processor. The memory may be present inside or outsidethe processor and may be connected with the processor through variouswell-known means.

In the aforementioned exemplary system, methods have been describedbased on flowcharts as a series of steps or blocks, but the methods arenot limited to the order of the steps of the present invention and anystep may occur in a step or an order different from or simultaneously asthe aforementioned step or order. Further, it can be appreciated bythose skilled in the art that steps shown in the flowcharts are notexclusive and other steps may be included or one or more steps do notinfluence the scope of the present invention and may be deleted.

What is claimed is:
 1. A method for a base station providing a machineto machine (M2M) service in M2M communication, the method comprising:receiving an update request message from an M2M device, the requestmessage requesting update of an M2M group identifier (MGID) andincluding the MGID and an M2M zone identifier, the MGID identifying aservice flow shared by a group of M2M devices in an M2M group zone andthe M2M zone identifier identifying the M2M group zone; and transmittinga response message to the M2M device in response to the received requestmessage, the response message including a service unavailabilityindicator that indicates whether the identified service flow is providedin the identified M2M group zone.
 2. The method of claim 1, wherein: theresponse message is transmitted according to Institute of Electrical andElectronics Engineers (IEEE) 802.16 based a dynamic service change (DSC)procedure when the M2M device is in a connected mode.
 3. The method ofclaim 1, wherein: the response message is transmitted according toInstitute of Electrical and Electronics Engineers (IEEE) 802.16 based aRNG-RSP (Ranging-Response) message when the M2M device is in an idlemode.
 4. A method for an M2M device providing a machine to machine (M2M)communication, the method comprising: acquiring an M2M group identifier(MGID) and an M2M zone identifier, the MGID identifying a service flowshared by a group of M2M devices in an M2M group zone and the M2M zoneidentifier identifying the M2M group zone; verifying whether the M2Mdevice leaves the M2M group zone; transmitting an update request messagethat requests update of the MGID when the M2M device leaves the M2Mgroup zone; and receiving a response message from a base station (BS) inresponse to the update request message, the response message including aservice unavailability indicator that indicates whether the identifiedservice flow is provided in the identified M2M group zone.
 5. The methodof claim 4, wherein: the response message is received according toInstitute of Electrical and Electronics Engineers (IEEE) 802.16 baseddynamic service change (DSC) procedure when the M2M device is in aconnected mode.
 6. The method of claim 4, wherein: the response messageis transmitted according to Institute of Electrical and ElectronicsEngineers (IEEE) 802.16 based a RNG-RSP (Ranging-Response) message whenthe M2M device is in an idle mode.
 7. The method of claim 4, furthercomprising: retaining the MGID and deferring the identified service flowwhen the service unavailability indicator indicates that the identifiedservice flow is not provided.
 8. The method of claim 7, furthercomprising: monitoring whether the M2M device reenters the M2M groupzone; and transmitting a resuming request message to the BS requestingthat the identified service flow be resumed when the M2M device reentersthe M2M group zone.
 9. The method of claim 7, further comprising:monitoring whether the M2M device reenters the M2M group zone; andtransmitting a resuming notification message to the BS notifying thatthe identified service flow is resumed when the M2M device reenters theM2M group zone.
 10. The method of claim 7, further comprising:monitoring whether the M2M device reenters the M2M group zone; andactivating an MGID retain timer indicating a time that the MGID isretained when the M2M device reenters the M2M group zone.
 11. The methodof claim 10, further comprising: releasing the MGID after the timeindicated by the MGID retain timer elapses.
 12. A machine to machine(M2M) device in an M2M communication system, the device comprising: aradio frequency (RF) unit configured for transmitting or receiving aradio signal; and a processor operatively coupled to the RF unit, theprocessor configured for: acquiring an M2M group identifier (MGID) andan M2M zone identifier, the MGID identifying a service flow shared by agroup of M2M devices in an M2M group zone and the identified M2M zoneidentifier identifying the M2M group zone; verifying whether the M2Mdevice leaves the identified M2M group zone; transmitting an updaterequest message that requests update of the MGID when the M2M deviceleaves the identified M2M group zone; and receiving a response messagefrom a base station (BS) in response to the update request message, theresponse message including a service unavailability indicator thatindicates whether the identified service flow is provided in theidentified M2M group zone.
 13. The M2M device of claim 12, wherein theprocessor is further configured for; retaining the MGID and deferringthe identified service flow when the service unavailability indicatorindicates that the identified service flow is not provided.
 14. The M2Mdevice of claim 12, wherein the processor is further configured for;monitoring whether the M2M device reenters the M2M group zone; andtransmitting a resuming request message to the BS requesting that theidentified service flow be resumed when the M2M device reenters the M2Mgroup zone.
 15. The M2M device of claim 12, wherein the processor isconfigured for; monitoring whether the M2M device reenters the M2M groupzone; and resuming the identified service flow when the M2M devicereenters the M2M group zone.
 16. The M2M device of claim 13, wherein theprocessor is further configured for; monitoring whether the M2M devicereenters the M2M group zone; and activating an MGID retain timerindicating a time that the MGID is retained when the M2M device reentersthe M2M group zone.
 17. The M2M device of claim 16, wherein theprocessor is further configured for; releasing the MGID after the timeindicated by the M2M group identifier retain timer elapses.